The present invention relates to a transmission bandwidth control technology in a network.
Generally, there are quality guaranty traffic forwarding methods and quality non-guaranty traffic forwarding systems as conventional technologies related to the transmission across the network.
Of the forwarding methods, for example, a Diffserv (Differentiated Services) system, an Intserv (Integrated. Services) system and an MPLS (Multi Protocol Label Switching) QoS (Quality of Service) path system, are given as the quality guaranty traffic forwarding systems on IP (Internet Protocol) networks.
Of the quality guaranty traffic forwarding systems, in the Diffserv system, an ingress router in the network distinguishes between traffic types, effects marking on a packet, and also restricts an inflow quantity of the traffic in accordance with a type of the packet. Further, in the Diffserv system, a priority is determined based on the traffic type. Therefore, the intra-network router forwards the packet according to this priority. This enables, in the Diffserv system, a quality of the quality guaranty traffic to be guaranteed.
Moreover, of the quality guaranty traffic forwarding systems, in the Intserv system, each router ensures a requested bandwidth for every flow by previously using an RSVP (Resource Reservation Protocol) protocol, whereby the quality can be maintained. Further, the Intserv system has a traffic control mechanism that rejects a request for the flow impossible of a bandwidth reservation by admission control, and guarantees the bandwidth for a queue in the router.
Further, of the quality guaranty traffic forwarding systems, in the MPLS (Multi Protocol Label Switching) QoS path system, each router ensures the bandwidth by use of RSVP-TE when a LSP is set up and allocates the quality guaranty traffic to the path, thereby making it possible to guarantee the quality of the quality guaranty traffic.
By the way, in the quality guaranty services, there might be a case where the path can not be set up on an optimal route depending on a traffic condition. For example, when the path can not be set up, a service providing side performs a service on a detour route. Further, in the case of being unable to ensure the bandwidth just when a quality guaranty traffic request is given from a terminal, in the quality guaranty traffic forwarding system, normally a call loss occurs.
For avoiding such a problem in these quality guaranty traffic forwarding systems, there is a method of reducing a call loss ratio by reallocating the existing flow to by far the shortest route. According to this method, a minimum-cost route is calculated for the quality guaranty traffic request from the terminal. At this time, when the calculated route contains only one link unable ensures the bandwidth, one flow contained in that link is selected. Then, this method schemes to make a reallocation to by far the different shortest route. When the route can be set up through this reallocation, there decreases the call loss of the request from the terminal.
Further, as non-guaranty traffic forwarding systems, there are hop-by-hop forwarding on a shortest route base and a dynamic load balancing system using multi-paths.
Of the non-guaranty traffic forwarding systems, in the hop-by-hop forwarding on the shortest route base, the shortest route is selected by a route search mechanism of IGP (Interior Gateway Protocol) such as OSPF (Open Shortest Path First). Then, the selected shortest route is reflected in a routing table of the router. At this time, the packets are forwarded packet by packet to a next hop while referring to the routing tables of the respective routers.
Further, of the non-guaranty forwarding systems, in the dynamic load balancing method using the multi-paths, the present inventors propose technologies of setting up a plurality of paths by MPLS and forwarding in a way that shares the traffic with the respective paths.
Moreover, the present inventors propose such a technology that functions required for the load balancing are distributed and allocated to a centralized control server and to the routers, and the function used as the necessity arises is switched over between the server and the router, thereby flexibly actualizing the centralized control and the distributed control.
First, generally the router for carrying out the existing systems forwards the guaranty traffic in preference to the non-guaranty traffic in order to guarantee a high throughput and a low delay of the quality guaranty traffic. Accordingly, in the case of letting the quality guaranty traffic and the non-guaranty traffic flow to the same link, as a quantity of the quality guaranty traffic increases, a quantity of the non-guaranty traffic that can be forwarded is restricted. Namely, the existing system has less of residual bandwidths for the non-guaranty traffic.
Therefore, in the non-guaranty traffic, when letting large quantity of packets, some are discarded due to the queue in the router.
Moreover, also in a case where there are links across which a large quantity of non-guaranty traffic flows, the existing system accepts and lets the quality guaranty traffic without considering that the large quantity of packets of non-guaranty traffic are to be discarded.
Still further, even by performing a link extension or raising a link speed in order to avoid discarding the packets of the non-guaranty traffic, as the link does not always come to state of congestion, it follows that a link using efficiency becomes lower than before the extension. Further, in this case, a problem was a rise in cost for the link extension.
Moreover, in the existing system, the quality guaranty path was not always set up on the best route, depending on the traffic condition. Then, in the existing system, there was a case in which if the bandwidth, though unable to ensure the bandwidth on the shortest route, can be ensured on a detour route, the detour route is to be selected.
As a system for steering clear of this problem, there is disclosed a technology of scheming to reallocate, when the requested quality is not met, the existing quality guaranty flow, i.e., the quality guaranty path to the best path.